CC115LRGPR datasheet(23/74 Pages) TI2

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Preamble bits

(1010...1010)

Data Field

Optional CRC-16 Calculation

8 x nbits

16 /32 bits

bits

8 x n bits

16 bits

Legend:

Inserted automatically

Optional user-provided fields (the length field is

processed by the radio)

Unprocessed user data

CC115L

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SWRS105B – MAY 2011 – REVISED JUNE 2014

5.8

Packet Handling Hardware Support

The CC115L has built-in hardware support for packet oriented radio protocols. The packet handler can be

configured to add the following elements to the packet stored in the TX FIFO:

•

A programmable number of preamble bytes

•

A two byte synchronization (sync) word. Can be duplicated to give a 4-byte sync word. It is not

possible to only insert preamble or only insert a sync word

•

A CRC checksum computed over the data field.

•

In a system where the CC115L is transmitting packets to the CC110L, CC113L or CC1101, the

recommended setting is 4- byte preamble and 4-byte sync word, except for 500 kBaud data rate where

the recommended preamble length is 8 bytes.

NOTE

is in the IDLE state.

5.8.1

Packet Format

The format of the data packet can be configured and consists of the following items (see Figure 5-6):

•

Preamble

•

Synchronization word

•

Optional length byte

•

Optional address byte

•

Payload

•

Optional 2 byte CRC

Figure 5-6. Packet Format

The preamble pattern is an alternating sequence of ones and zeros (10101010…). The minimum length of

the preamble is programmable through the value of MDMCFG1.NUM_PREAMBLE. When enabling TX,

the modulator will start transmitting the preamble. When the programmed number of preamble bytes has

been transmitted, the modulator will send the sync word and then data from the TX FIFO if data is

available. If the TX FIFO is empty, the modulator will continue to send preamble bytes until the first byte is

written to the TX FIFO. The modulator will then send the sync word and then the data bytes.

The synchronization word is a two-byte value set in the SYNC1 and SYNC0 registers. If the CC110L,

CC113L, or CC1101 are used at the receiving end, they will need the sync word for byte synchronization

of the incoming packet. The synchronization word is automatically inserted by the CC115L. A one-byte

sync word can be emulated by setting the SYNC1 value to the preamble pattern. It is also possible to

emulate a 32 bit sync word by setting MDMCFG2.SYNC_MODE to 3. The sync word will then be repeated

twice.

CC115L supports both constant packet length protocols and variable length protocols. Variable or fixed

packet length mode can be used for packets up to 255 bytes. For longer packets, infinite packet length

mode must be used.

Detailed Description

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